Laminated magnetic element



May27, 1941- G. w. RAWLINGS 2,243,318

LAMINATED MAGNET I C ELEMENT Filed Oct. 27, 1938 3 Sheets-Sheet l fl & 351216 a A fi o 13 his 41701726]: W ww.

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LAMINATED MAGNETIC ELEMENT Filed Oct. 2'7, 1938 3 Sheets-Sheet 5Patented May 27, 1941 LAMINATED MAGNETIC ELEMENT George WilliamRawlings, Willow Meer, Kenilworth, England Application October 27, 1938,Serial No. 237,290 In Great Britain November 1, 1937 11 Claims.

This invention relates to laminated magnetic elements used in theconstruction of imbricated type armature and field cores, and otherimbricated type magnetic circuits. The term imbricated type armature orfield core" is herein used to define the known type of armature or fieldcore construction wherein the alternate poles are formed by theinterdigitation of two sets of pole pieces. each set having a commonyoke of such a form that when the two sets of pole pieces areinterdigitated the magnetic circuit between themcan be completed in sucha manner that the iron circuit so formed can embrace a coil windingdisposed concentric with the axis of the core and flux-linked with thetwo sets of interdigitated pole pieces.

It is an object of the present invention to provide an improvedconstruction of laminated imbricated type armature or field core and alaminated magnetic element used in forming such cores. The laminatedmagnetic element of or for the laminated imbricated type armature orfield core of the invention comprises a plurality of laminations-nestedone within another, each laminationhaving a yoke and a plurality of polepieces extending laterally from the yoke, the polepieces forming poles,each having a pole surface formed largely by end portions of the polepieces. The pole pieces preferably have bevelled ends and when thelaminations are nested together the pole pieces form poles and thebevelled ends collectively form a pole surface for each pole.

In the accompanying drawings:

Fig. 1 is a part sectional side elevation of a laminated magneticelement forming one-half of a 4-pole imbricated armature core.

Fig. 2 is a front elevation of the core of Fig. 1.

Fig. 3 is a plan of the laminated magnetic element of Fig. 1.

Fig. 4 is a plan showing a modification of Fig. 3.

Figs. 5 and 6 are sectional and front elevations of a 20-pole imbricatedarmature core.

Fig. 5a is a modified form of the core of Figs. 5 and 6.

Figs. 7 and 8 are sectional and part side elevations of a furtherexample of the invention.

Figs. 9 and 10 are developed plans of alternative pole forms.

Fig. 11 is a fragmentary perspective view illustrating an alternativeform of pole piece.

Fig. 12 is a perspective view with parts removed illustrating arotorformed of the laminated elements of Figs. 1, 2 and 3.

As illustrated in Figs. 1 to 3, the laminated magnetic element isone-half of a 4-pole imbricated armature core as shown in Fig. 12 andcomprises 5 laminations, a, b, c, d, and 2, each of which issubstantially U-shaped with flat yoke a", b, c", d, and e having acentral hole I by which the laminations are ultimately assembled on aspindle. The laminated magnetic element has an armature axis C throughthe hole I which is concentric with the center of the spindle or shaftupon which the magnetic element is to be mounted. Each lamination hasalso a pair of arms or pole pieces a, b 0 d and e bent laterally withrespect to their respective ycses and inclined with respect to thearmature axis C which are of curved cross-section, and the bevelled endsa b 0 d and e form collectively two cylindrical or arcuate shaped polesurfaces. The pole pieces as assembled together form separate poles Aand B, each of which has a pole surface formed substantially of thebevelled ends of the separate pole pieces. Each bevelled end is,therefore, a part of the pole surface.

The divisional lines 9 of the pole surface formed by the adjoiningbevelled ends of the laminations are substantially parts of circles inplanes at right angles to the armature axis, and in Fig. 3 appear asstraight lines parallel to the planes of the yoke parts of thelaminations and this is. due to the formation of the curved inner facesof the arm as conical surfaces coaxial with the cylindrical outer Dolesurface. The shape and direction of the lines 9' may obviously be variedby altering the shape of the inner faces and therefore changing theformation of the lines of intersection.

Further division of the pole surfaces may be obtained, as shown in Fig.4, by cutting one or more narrow slots h, in the arms which may besubstantially closed in the bending operation.

A simple and preferred method of manufacture consists in super-imposingand assembling 5 equal lamination stampings on a locating pin at the endof a conical plug and shaping the laminations by one forming and onecutting operation by forcing the plug first into a taper-forming die andthen through a ring shearing die. The outer cylindrical surfaces of theassembly, that is, the pole surfaces, may be formed by grinding oil theends of the pole pieces, forming the bevelled ends, which collectivelycomprise a pole surface.

As shown in Figs. 5 and 6, the 20-pole imbricated armature core isformed of a pair of interdigitated laminated magnetic elements i and 1,the poles i and j of which are formed in the same manner as the poles ofthe 4-pole armature described above and the magnetic circuit betweenalternate poles is completed through inwardly turned annular flanges iand 9' which engage each other with substantial edge register betweencomplementary laminations on the centre line k. The engaging end facesof these flanges i and 7' may be ground to reduce air gap reluctance.The yokes i and i of the core elements are more or less at right anglesto the spindle p and extend from the flanges to the pole pieces 1 and iIn the modification Fig, 5a, the engagement lines of the flanges of theseveral laminations are stepped as at W, so that the flanges areinterleaved. In this form also the pole pieces may be slotted in thesame manner as the pole illustrated in Fig. 4 for further division ofthe pole surface.

In Figs. '7 and 8 the invention is shown applied a magneto electricmachine of the type in the armature core L encircles a permanent etfield core N. In this construction Z and pair of interdigitatedlaminated magnetic core elements, each having six poles L and L the pairof elements being secured together with an electric coil m embracedbetween them and with the pole pieces equally spaced apart, suchassembly forming the armature. Each core element is formed of aplurality of laminations having yokes L and L flanges L and L bent atright angles to the yokes and poles L and L inclined with respect to theyokes similar to the poles of Figs. 1 to 3. The flanges join along theline k where the contact is such as to establish a good magneticcircuit. The field magnet core N comprises a pair of interdigitatedlaminated magnetic elements n and 11. each having six poles N and Nassembled together to embrace a cylindrical permanent magnet secured toa shaft or spindle 1), preferably of non-magnetic material. Eachmagnetic element is formed of a plurality of laminations including ayoke n having a hole by means of which the element is mounted upon thespindle p. The yokes are preferably at right angles to the axis of thespindle and the pole pieces of the poles are bent laterally with respectto the yokes and have pole surfaces similar to those of Figs. 1 to 3which are arcuate and concentric to the spindle p. The cylindricalmagnet is magnetised axially so that the alternate laminated pole piecesof the assembly are of opposite polarity. The construction thereforeprovides 12 reversals of polarity for each revolution of the armature.

When the construction is adapted for the purpose of a spark ignitionmagneto, the single coil m would be replaced by the necessary primaryand secondary coils.

It will be appreciated that the permanent magnet 0 could be replaced byan electro-magnet coil, in which case the laminated elements n and nwould preferably be constructed with annular flanges at the bore similarto those shown at i and 1' in Fig. 5 to complete the magnetic circuitindependently of the shaft 9. A motor or generator of this form could bearranged for either A. C. or D. C. working by the provision of suitablemeans of commutation or rectification.

In Figs. 9 and 10, are shown alternative pole forms, the relativeeffects and advantages of which will be known to a person familiar withthe design of generators or motors, the poles q in Fig. 9 being taperedwhilst the poles r of Fig. 10 are parallel sided.

The laminated magnetic element illustrated in Fig. 11 comprises aplurality of laminations e, u

and 12 having yokes a and 12 arranged at right angles to the axis C ofthe hole 3' by means of which the element is mounted upon a spindle. Thepole pieces t u and 11 extend laterally with respect to the yokes andhave arcuate surfaces t u and v The pole pieces in their groupedarrangement form a pole and the arcuate surfaces thereof collectivelyform a pole surface.

The rotor illustrated in Fig. 12 is formed of two interdigitatedlaminated magnetic elements similar to those of Figs. 1 to 3. A sleeveor tube T is inserted in the hole 1 of the magnetic elements and thistube is reduced in diameter at its ends to form a slight shoulderagainst which the laminations are located and then the outer end of thetube is swaged over to secure the laminations thereon. It is, of course,understood that the bobbin is fitted on the tube between the sets oflaminations before they are secured together. It is further understoodthat any other suitable means may be used for securing the laminationstogether, and in relation with respect to each other and the spindle,such as a threaded bushing and nuts, nuts screwed over a threadedspindle bearing against the laminations, or by pressing the laminationsover the spindle to a snug fit.

As will be seen, in all forms of the core, the area of the pole surfaceis at least twice the minimum cross sectional area of the laminationsand the laminations substantially follow the flux path in the core, andwhere more than 4 poles are provided, each lamination resembles a cupwith castellated side.

It will be seen from the drawings that the laminations are formed ofpieces of thin metal having broad surfaces and narrow edge surfaces. Theterm broad surface used in some of the claims refers to the kind ofsurfaces which are in contact by reason of the nesting of thelaminations. As shown in the drawings the laminations are so arrangedthat the broad surfaces of the yokes are transverse to the longitudinalaxis of the spindle.

The armature core construction such as shown in Figs. 1 to 5 may withadvantage be combined with the invention described in my copendingapplication Serial No. 141,669, flied May 10, 1937. That is to say, itis known that an imbricated armature of itself provides a loadvoltage/speed limitation due to its different internal flux path anddifferent internal flux leakage paths as compared with a non-imbricatedarmature, but in spite of this difference an appreciable advantage inimproved load voltage/speed control is obtainable from the saidcombination.

What I claim is: U

1. A laminated magnetic element for an imbricated magnetic corecomprising a plurality of laminations nested one within another, thelaminations having pole pieces which form poles each of which has a polesurface, said pole pieces being inclined to the pole surface and havingtheir ends bevelled so as collectively to form such pole surface, eachlamination being substantially of the form of a conical cup withcastellated side.

2. A laminated magnetic element for an imbricated magnetic corecomprising a plurality of laminations nested one within another, eachlamination having two or more pole pieces which collectively form poleseach having a pole surface, the area of the pole surface being at leasttwice the minimum cross sectional area of the laminations, and each polepiece being divided by a slot. 1

3. A laminated imbricated magnetic core comprising two separateinterdigitated laminated magnetic elements each including a plurality oflaminations having a plurality of pole pieces, a yoke. and a flangeportion, the pole pieces forming poles, each pole having a pole surfaceformed of end portions of the pole pieces, the ends of the flangeportions of the laminations of the two elements uniting with substantialend register establishing a magnetic circuit between the two elements.

4. A laminated imbricated magnetic core comprising two separateinterdigitated magnetic elements each formed of a plurality oflaminations having pole pieces and a yoke, the laminations being nestedtogether so that the pole pieces form poles, each pole having a polesurface comprising end portions of the pole pieces, said pole piecesextending laterally with respect to the yoke, and means for mounting theelements on a spindle with the laminations of the two elements inmagnetic contact and the poles interdigitated spaced relation.

5. A laminated magnetic element arranged to be mounted around a spindlewhich comprises a plurality of laminations nested one within another,each lamination having a yoke the broad surfaces of which are transverseto the longitudinal axis of the spindle and pole pieces, each of saidpole pieces being inclined with respect to the yoke, the ends of thepole pieces being bevelled and collectively form a pole surface for theelement.

6. A laminated magnetic element arranged to be mounted around a spindlewhich comprises a plurality of laminations nested one within another,each lamination having a yoke the broad surfaces of which are transverseto the longitudinal axis of the spindle and pole pieces, each of saidpole pieces extending laterally from the yoke and having a surface ofarcuate form, the pole pieces forming poles for the element, each polehaving a pole surface comprising the separate adjoining surfaces of thepole pieces.

'7. A laminated magnetic element which comprises a plurality oflaminations nested one within another, each lamination having a yoke andpole pieces, a. spindle upon which the nested laminations are mounted,each of said pole pieces extending laterally from the yoke and having abevelled end surface of arcuate form concentric with the axis of thespindle, the laminations nested together being so arranged that the polepieces are grouped together forming poles, each pole having a polesurface comprising arcuate surfaces of the pole pieces.

8. A laminated magnetic element for an imbricated magnetic core arrangedto be mounted around a spindle which comprises a plurality oflaminations nested one within another, each lamination having a broadsurface transverse to the longitudinal axis of the spindle, eachlamination having two or more pole pieces which form poles, each polehaving a pole surface. said pole pieces being inclined to the broadsurfaces and having their ends beveled so as collectively to form thepole surfaces.

9. A laminated magnetic elementfor an imbricated core arranged to bemounted around a spindle which comprises a plurality of laminationsnested one within another, each lamination having a yoke the broadsurfaces of which are transverse to the longitudinal axis of the spindleand two or more pole pieces extending laterally from the yoke, the polepieces collectively forming poles each having a pole surface formed ofend portions of. the pole pieces. the area of the pole surface being atleast twice the maximum cross-sectional area of the lamina tions.

10. A laminated imbricated magnetic core as defined in claim 4 in whicheach lamination is so arranged with respect to the longitudinal axis ofthe'splndle that the broad surface of the yoke is transverse to the saidaxis and the pole pieces are so bent that the broad surfaces thereof arearcuate and concentric with the said axis.

11. A laminated imbricated magnetic core as defined in claim '7 in whicheach lamination is so arranged with respect to the longitudinal axis ofthe spindle that the broad surface of the yoke is transverse to the saidaxis and the pole pieces are so bent that the broad surfaces thereof arearcuate and concentric with the said axis.

GEORGE W. RAWLINGS.

CERTIFICATE OF commcmou. Patent No. 2,215,518. May 2 19!;1.

GEORGE wnum mwuuos.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows: Page 2,first column, line 75, for "e" after "laminations" read t--; p gfl 5,first column, line 1.1., claim 5, after "laminationfl insert the words--nested one within another, each lamination--; line 22, c .a1m h, after"poles" insert --in-; and that the said Letters Patent should be readwith this correction therein that the same may conform to the record ofthe case in the Patent 0:" ice.

Signed and sealed this 15th day of July, A. 1). 191m.

Henry Van Arsdale, (Seal) Acting Commissioner of Patents.

CERTIFICATE OF CORRECTION. v Patent No. 2,215,51 ma 27, 19!;1.

GEORGE WILLIAM RAWLINGS.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows: Page 2,first,

column, line 75, for "e" after "laminations" read --t--; page 5,' firstcolumn, line LL, claim 5, after "laminations" insert the words --nestedone within another, each lamination-; line 22, claim 11., after "poles"insert -in-; and that the said Letters Patent should be read with thiscorrec tion therein that the same may conform to the record of the casein the Patent Office.

Signed and sealed this 15th day of July, A. D. 19in.

Henry Van Arsdale, (Seal) I Acting Commissioner of Patents.

